Tracking of emergency personnel

ABSTRACT

Techniques are disclosed that allow for the detection, identification, direction finding, and geolocation of emergency personnel in a given multipath environment. For example, the techniques can be used to detect and identify multiple lines of bearing (LOBs) to an IEEE 802.11 emitter of an emergency responder that is inside a building or otherwise hidden from view. LOBs from multiple vantage points can be used to geolocate and/or track the emergency responder. The resulting geolocation can be plotted on a map display or model of the scene (e.g., building, etc) so the precise position of the emergency responder having the targeted wireless emitter can be known.

RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 12/487,469,filed Jun. 18, 2009, and titled “Direction Finding of Wireless Devices.”This application is also related to U.S. application Ser. No.12/487,511, filed Jun. 18, 2009, and titled “Direction Finding andGeolocation of Wireless Devices.” Each of these applications is hereinincorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to wireless communications, and more particularly,to techniques for direction finding and geolocating emergency personnelequipped with wireless devices such as those configured with IEEE 802.11emitters and other such detectable emitters.

BACKGROUND OF THE INVENTION

Conventional techniques for locating IEEE 802.11 emitters (e.g., accesspoints as well as laptops with IEEE 802.11 capability and other suchclients) are based on measuring the amplitude of the 802.11 emitter witha portable receiver, and moving around to find the direction in whichthe amplitude increases. The general assumption is that the stronger thesignal amplitude, the closer the 802.11 emitter is believed to be.Several commercial devices were developed for this purpose (e.g.,Yellowjacket® 802.11b Wi-Fi Analysis System).

There are a number of problems associated with such amplitude-basedtechniques for locating 802.11 emitters. For instance, the techniquestend to be highly inaccurate due to the incidence of RF multipathcreated by the RF waveforms emanating from the 802.11 emitters. Thesewaveforms bounce off conductive objects or surfaces in the environment,which causes multiple false readings on increased amplitude (falsedirections) that then disappear as the user leaves the multipath. Thus,conventional amplitude-based locationing techniques will create manyfalse high amplitude paths to the target that will be incorrect, andwill not work in a high multipath environment, such as a neighborhood(e.g., street scene) or building (e.g., home, office building, or café).

There is a need, therefore, for techniques that allow for the detection,identification, direction finding, and geolocation of wireless emittersin a given environment.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a method for trackingpersonnel at a scene. The method includes measuring one or more responsesignal parameters for each of Y antenna patterns, thereby providing a Ysample array of response data from a target wireless emitter of a personto be tracked (such as a personal cell phone or a dedicated wirelessemitter specifically used for tracking), wherein Y is greater than 1(e.g., Y=64 or 4096; any number of antenna patterns can be used). Themethod further includes correlating the sample array to a plurality ofentries in a database of calibrated arrays having known azimuths, todetermine a line of bearing (LOB) to the target wireless emitter. Themethod further includes repeating the transmitting, measuring andcorrelating to determine one or more additional LOBs to the targetwireless emitter, each LOB computed from a different geographiclocation, and geolocating the target wireless emitter based on the LOBs,thereby geolocating the person. The method may further include thepreliminary steps of surveying an area of interest to identify wirelessemitters within that area (e.g., using established discovery protocols),and selecting a target emitter discovered during the survey. Thisselection may be, for example, based on user input, or doneautomatically based on some established selection scheme. In oneparticular case, the target emitter is associated with a media accesscontrol (MAC) address and communication channel learned during thesurvey. Here, the method may further include transmitting a stimulussignal to the target emitter using the MAC address and communicationchannel. In another particular case, the correlating includes generatinga correlation plot having a peak using correlation factors resultingfrom correlation of the sample array to the plurality of entries in thedatabase, identifying a target azimuth of the sample array based on thepeak of the correlation plot, and determining the LOB to the targetwireless emitter based on the target azimuth. In some cases, each of theLOBs is associated with position and heading tags provided by a globalpositioning satellite (GPS) module to assist in geolocating the targetwireless emitter. The method may include graphically displayinggeolocations of the target wireless emitter. The method may includeperiodically repeating the geolocating of the target wireless emitter,thereby periodically geolocating the person as that person moves aroundthe scene. The one or more response signal parameters may include, forexample, response signal amplitude. The method can be carried out, forexample, using portable devices (e.g., vehicle-based, suitcase-based,and/or handheld devices) configured for performing the transmitting,measuring and correlating, and a command workstation (e.g.,vehicle-based, suitcase-based, and/or handheld devices) wirelesslycoupled to the portable devices is configured for performing thegeolocating.

Another embodiment of the present invention provides a system fortracking personnel at a scene. The system includes an antenna array formeasuring one or more response signal parameters for each of Y antennapatterns, thereby providing a Y sample array of response data from atarget wireless emitter of a person to be tracked, wherein Y is greaterthan 1. The system further includes a line of bearing module forcorrelating the sample array to a plurality of entries in a database ofcalibrated arrays having known azimuths, to determine a line of bearing(LOB) to the target wireless emitter. The system further includes ageolocation module for geolocating the target wireless emitter based onmultiple LOBs to the target wireless emitter, each LOB computed from adifferent geographic location, thereby geolocating the person. Thesystem may be further configured for surveying an area of interest toidentify wireless emitters within that area. In one such case, thesystem includes a user interface for allowing a user to select a targetemitter discovered during the survey. In another such case, the targetemitter is associated with a media access control (MAC) address andcommunication channel learned during the survey. In one such case, thesystem may further include a transceiver configured for transmitting astimulus signal to the target emitter using the MAC address andcommunication channel. In another example case, the line of bearingmodule is configured for generating a correlation plot having a peakusing correlation factors resulting from correlation of the sample arrayto the plurality of entries in the database, and identifying a targetazimuth of the sample array based on the peak of the correlation plot,and determining the LOB to the target wireless emitter based on thetarget azimuth. In another example case, each of the LOBs is associatedwith position and heading tags provided by a global positioningsatellite (GPS) module to assist in geolocating the target wirelessemitter. The system may include a user interface for graphicallydisplaying geolocations of the target wireless emitter, and/or adatabase for storing the geolocation of the target wireless emitter. Thegeolocation module can be configured, for example, for periodicallygeolocating the target wireless emitter, thereby periodicallygeolocating the person as that person moves around the scene. In oneexample case, the system includes a plurality of portable devices eachlocated at a different vantage point to the scene and configured with atransceiver, an antenna array, and an LOB module. Here, the system mayfurther include a command workstation wirelessly coupled to theplurality of portable devices and configured with the geolocationmodule. Alternatively, the system includes a single portable device thatis moved to provide different vantage points from which measurements canbe taken. Note that measurements can be taken while the system isstationary or moving. A number of variations on this system will beapparent in light of this disclosure.

The features and advantages described herein are not all-inclusive and,in particular, many additional features and advantages will be apparentto one of ordinary skill in the art in view of the drawings,specification, and claims. Moreover, it should be noted that thelanguage used in the specification has been principally selected forreadability and instructional purposes, and not to limit the scope ofthe inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless emitter locating system configured inaccordance with an embodiment of the present invention.

FIG. 2 a illustrates a detailed block diagram of the wireless emitterlocating system shown in FIG. 1, configured in accordance with anembodiment of the present invention.

FIG. 2 b illustrates further details of the wireless emitter locatingsystem shown in FIG. 2 a, configured in accordance with an embodiment ofthe present invention.

FIG. 2 c illustrates example states and modes of the wireless emitterlocating system shown in FIG. 2 a, in accordance with an embodiment ofthe present invention.

FIGS. 3 a and 3 b illustrate a vehicle-based version of the wirelessemitter locating system shown in FIG. 2 a, configured in accordance withan embodiment of the present invention.

FIG. 4 illustrates an example user interface of the wireless emitterlocating system shown in FIG. 2 a, in accordance with an embodiment ofthe present invention.

FIG. 5 a illustrates a method for determining a line of bearing to awireless emitter, and geolocating that emitter, in accordance with anembodiment of the present invention.

FIG. 5 b illustrates a correlation process carried out by the method ofFIG. 5 a, to identify which calibrated array best matches a samplearray, in accordance with an embodiment of the present invention.

FIG. 5 c illustrates a correlation scan or plot of correlationcoefficients resulting from the correlation process shown in FIG. 5 b,and having a peak that corresponds to an azimuth (or LOB) to the target,in accordance with an embodiment of the present invention.

FIG. 6 illustrates a system for direction finding, geolocating, andtracking emergency personnel, configured in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Techniques are disclosed that allow for the detection, identification,direction finding, and geolocation of emergency personnel in a givenmultipath environment. For example, the techniques can be used to detectand identify multiple lines of bearing (LOBs) to an IEEE 802.11 emitterattached to or otherwise possessed by the emergency responder that isinside a building or otherwise contained area not easily viewable fromthe outside. The LOBs from multiple vantage points can be used togeolocate and/or otherwise track the emergency responder. For instance,by integrating two or more of direction finding devices as describedherein via wireless network, and locating those devices on respectiveemergency response vehicles placed around an incident scene, theindividual LOBs can effectively be fused together to calculate a 3Dgeolocation (the geospacial intersection of 3 or more LOBs) of an IEEE802.11 emitter carried by an emergency responder inside a building. Theresulting geolocation can then be plotted on a map display or model ofthe building so the precise position in the building of the emergencyresponder having the targeted wireless emitter can be known.

General Overview

Wireless communication devices, which are typically configured with anetworking card or a built-in chip or chip set, are vulnerable tostimulation or otherwise exploitable for on-demand direction finding.Typical such wireless devices include, for example, laptops computers,cell phones and personal digital assistants (PDAs), access points andrepeaters, and other portable communication devices. In addition, suchdevices typically include a physical address (e.g., MAC address) bywhich they can be identified and subsequently directly communicatedwith.

In accordance with one embodiment of the present invention, a trackingsystem is provided for direction finding and geolocating wirelessdevices (e.g., IEEE 802.11 a/b/g/n/etc capable devices, all channels)worn by or otherwise possessed by emergency responders at the scene ofan incident (such as a building fire or other such situations requiringemergency responders to move within an area having no or poor visibilitysuch that visually tracking their movement is not possible). Thetracking system generally includes a plurality of vehicle-based wirelessemitter locating systems, each wirelessly coupled to a mesh network thatalso includes a command workstation that receives LOBs and any otherpertinent information and uses that information to track the emergencyresponder associated therewith, as will be explained in turn. Thewireless emitter locating systems may be integrated, for example, intoemergency responder vehicles (fire truck, police car, ambulance, etc).Alternatively, or in addition to, the wireless emitter locating systemsmay be contained in self-contained suitcases that can be deployed alongthe perimeter or otherwise suitably located at a scene. Alternatively,or in addition to, the wireless emitter locating systems may becontained in a handheld unit that can be used by someone tasked withtracking emergency responders at a scene.

Each of these wireless emitter locating systems (whether vehicle-based,handheld, etc) generally includes a wireless transceiver, a switchableantenna array, and a direction finding algorithm that correlatesmeasured responses with calibrated responses to continuously identify anLOB to a target wireless device associated with an emergency responderas that emergency responder moves around at the scene. The variouscomputed LOBs (along with relevant data, such as time stamp and GPSposition and heading tags) are communicated to the command workstationvia the mesh network, which uses the LOBs to geolocate and/or otherwisetrack the emergency responder. The command workstation can beconfigured, for instance, similarly to the individual wireless emitterlocating systems, but further includes the capability to receiveinformation (LOBs, etc) published to the network and to compile andpresent that information in a useful manner. The various wirelessdevices (and their corresponding emergency responders) in the trackingsystem's field of view (FOV), such as cell phones of the emergencyresponders and/or dedicated wireless emitters sewn into the emergencyresponder's gear, can be targeted based on their specific MAC address(or other suitable physical address or identifier), thereby allowing forindividual tracking of each emergency responder at a scene.

In operation, the tracking system may initially carry out a surveyprocess once deployed in the field, where each of the wireless emitterlocating systems discovers or otherwise detects wireless emitters (andhence a corresponding emergency responder) in its FOV. For instance,IEEE 802.11 discovery protocols can be used by the tracking system todiscover and handshake with each emitter in its FOV. During thisdiscovery process, the wireless emitter locating system learnsinformation associated with the various emitters, such as the emitter'smedia access control (MAC) address, service set identifier (SSID),and/or communication channel. In other embodiments, a network detectorcan be used to unobtrusively detect and interpret information beingtransmitted by wireless emitters in the FOV. Once this survey process iscompleted, the discovered wireless emitters and their respectiveinformation are reported to the command station. The tracking system canthen selectively target each of the discovered emitters (andcorresponding emergency responders) for continuous direction finding,geolocation, and tracking as they move throughout the scene.

For instance, each of the wireless emitter locating systems is capableof transmitting a stimulus signal (e.g., an IEEE 802.11 compliant RFsignal, or any suitable signal that will cause a desired responsesignal) to stimulate a target emitter based on that emitter's MACaddress, and captures the response from the target emitter.Alternatively, or in addition to, each of the wireless emitter locatingsystems may be capable of passively listening to target emitters thatare capable of automatically broadcasting their existence and pertinentinformation (e.g., pilot or beacon signal) in accordance with adiscovery protocol (i.e., no stimulus signal is required). To facilitatedescription herein, such automatic broadcast signals can be thought ofas a response as well, even though no stimulus signal is required. Inany such cases, the switchable antenna array of the wireless emitterlocating system operates in synchronization with a transceiver, andallows for response signal detection over numerous antenna arrayconfigurations.

For example, an antenna array having six horizontally-polarizedswitchable elements has up to 64 different configurations (i.e., 2⁶).Other antenna array configurations will be apparent in light of thisdisclosure. In any such cases, one or more response signal parameters(e.g., amplitude, or amplitude and phase) can be detected for each ofthe Y antenna array configurations, so as to provide an array (having Yentries) of response signal data associated with the target emitter. Thewireless emitter locating system's direction finding algorithm operatesto convert this array of measurements into an LOB relative to thecurrent position and orientation of array, and publishes those LOBs tothe mesh network.

The geolocation algorithm at the command station operates tocontinuously accumulate LOBs and geolocate the precise location of theemitter (based on an intersection of the LOBs computed from multiplevantage points and/or global positioning satellite (GPS) position andheading tags associated with each computed LOB). The continuous LOBand/or geolocation can be communicated to a user (e.g., personresponsible for monitoring the command work) station, for example, via adisplay or other suitable user interface. In one particular suchembodiment, results can be visually depicted on a map display or polarplot to indicate in real-time the direction to and/or location of thetarget device. Likewise, the results can be projected onto a model ofthe structure where the emergency responders are deployed, if sodesired. The user interface may be further configured to allow forcontrol and tasking of the system, as will be apparent in light of thisdisclosure.

The tracking system and techniques do not interfere with service to thetarget device (operation is effectively transparent to target device).In addition, the techniques work at the hardware layer regardless ofdevice mode, thereby bypassing various impediments such as encryptiontechniques, MAC address filters, and hidden SSIDs. The tracking systemand techniques can be used for a number of geolocation and/or trackingapplications, such as locating or tracking personnel in rural and urbanenvironments, or within a military zone.

A number of system capabilities and features will be apparent in lightof this disclosure. For instance, the individual wireless emitterlocating systems of the tracking system can be implemented in a compactfashion thereby allowing for form factors amenable to suitcase-based,handheld, vehicle-based or unmanned aerial vehicle (UAV) configurations,and can be employed to survey, detect, identify, direction find,geolocate, and/or track wireless emitters (e.g., 802.11 access pointsand clients, cell phones, PDAs, etc). The LOB to and/or geolocation ofsuch target emitters can be identified from within the same building orfrom outside a building or in an outdoor area or other multipathenvironments (at ground level, aerial, etc) thereby providing thecapability for precise locationing and tracking.

Other emitters that broadcast their existence and/or are vulnerable tostimulation (e.g., Bluetooth emitters) and characterization can bedetected using the techniques described herein, and the presentinvention is not intended to be limited to IEEE 802.11 emitters. Inaddition, note that the number of antenna configurations provided byeach of the wireless emitter locating systems will depend on the numberof switchable elements included in the array and whether or not thoseelements are vertically-polarized and/or horizontally-polarized. Forinstance, an antenna array having six switchable elements that are eachboth vertically-polarized and horizontally-polarized has up to 4096different configurations (i.e., 2¹²).

Wireless Emitter Locating System

FIG. 1 illustrates a wireless emitter locating system 10 configured inaccordance with an embodiment of the present invention. The system 10can be implemented, for example, in a handheld-based platform,vehicle-based platform, or suitcase-based platform to allow for portabledirection finding, geolocationing, and/or personnel tracking inmultipath environments. As will be apparent in light of this disclosure,a number of systems 10 can be wirelessly coupled to provide a personneltracking system, an example of which is shown in FIG. 6. Note that somesystems 10 included in such a tracking system may be configureddifferently from others. For instance, not all systems 10 have to beconfigured to compute geolocations. Rather, a command workstation towhich all computed lines of bearing, position data, and timinginformation are transmitted can be configured to compute the geolocationand to provide a map or other suitable user display having the person'slocation indicated thereon.

As can be seen, system 10 is capable of transmitting stimulus signals toits field of view (FOV), and receiving responses (or broadcast signalsused in discovery process) from any number of wireless emitter devices50 located in that FOV. The example wireless emitter devices 50 depictedinclude laptop 50 a, PDA 50 b, cell phone 50 c, and wireless accesspoint 50 d, and a personnel tracking emitter 50 e. Each of these devices50 can be, for example, IEEE 802.11 compliant wireless emitters. In amore general sense, devices 50 can operate in accordance with anywireless communication protocol that allows, for instance, discoverybased on an established handshake or other messaging technique by whichdevices 50 and system 10 make their existence known to each other toestablish communication links there between. Other detection techniques,whether based on such two-way messaging schemes or one-way covertdetection mechanisms, will be apparent in light of this disclosure.

Thus, system 10 may initially transmit a stimulus signal to survey thecurrently available devices 50. The survey signal transmitted by system10 may be responsive to signals being transmitted by the devices 50, ormay be the initiating signal that wakes-up devices 50 so that they canrespond in accordance with an established wireless communicationsprotocol. During such discovery processes, the devices 50 may shareinformation about themselves with system 10. For instance, devices 50that are compliant with IEEE 802.11 may share information includingtheir MAC address, SSID, channel, and current encryption status (e.g.,encrypted or not encrypted). In other embodiments, the discovery processcan be covert or otherwise transparent to the wireless emitters 50 inthe FOV. For instance, a network detector (such as KISMET orNETSTUMBLER) can be used to detect and interpret information beingtransmitted by wireless emitters in the FOV, thereby allowinginformation such as MAC address, SSID, channel, and current encryptionstatus to be identified. Thus, pertinent information about the potentialtarget wireless emitters 50 in the system's FOV can be acquired by asurvey that uses at least one of discovery protocols and/or networkdetection techniques, and the system 10 can then communicate withspecific ones of the various available target wireless devices 50, so asto direction find and/or geolocate that target device.

The devices 50 can be located, for example, in a building or outdoors ina park area or along a roadside. The system 10 can be located in thesame building, a different building, or outside as well. In short,system 10 can direction find and geolocate devices 50 regardless of theenvironment (multipath or not) associated with the respective locationsof system 10 and devices 50. As explained herein, when a person such asan emergency responder carries, or is otherwise outfitted with, awireless emitter device 50, that person's location can be tracked by atracking system that includes a number of the systems 10. The distancebetween each system 10 and devices 50 can vary depending on factors suchas transmit power and the communication protocols employed. In anembodiment using IEEE 802.11 communication protocols, the distance canbe, for instance, out to hundreds of meters.

FIG. 2 a illustrates a detailed block diagram of the wireless emitterlocating system 10, configured in accordance with an embodiment of thepresent invention. As previously explained with reference to FIG. 1, thesystem 10 is capable of identifying potential target emitter devices,and computing one or more LOBs to a target device. The system can thengeolocate the target device on the LOB, based on an intersection of LOBsfrom multiple vantage points and/or GPS position and heading tagsassociated with each computed LOB, as will be discussed in turn. Thisgeolocation capability can be provisioned, for example, to a commandworkstation to which LOBs are communicated via a wireless network, asbest shown in FIG. 6.

As can be seen in FIG. 2 a, the system 10 generally includes a computer200, a multi-element beamforming array 216, a GPS module 213 and GPSantennas 213 a-b, a network detector 215 and omni-directional surveyantenna 215 b, an Ethernet hub 219, and an optional mapping module 221.The multi-element beamforming array 216 includes an RF transceiver 217and a beamformer 218 that includes an RF switching network 218 a and amulti-element antenna array 218 b. The computer 200 includes a userinterface 201 having controls 201 a and display area 201 b, a processor203, and a memory 205. The memory 205 of this example embodimentincludes calibration files 209, a LOB module 207, and a geolocation(Geo) module 211. Other conventional componentry not shown will beapparent in light of this disclosure (e.g., busses, storage mechanisms,co-processor, graphics card, operating system, user interfacemechanisms, etc). The system may be powered by batteries, or may deriveits power from other sources, such as a vehicle in which the system isoperating. A number of suitable power schemes can be used here.

The RF transceiver 217 generates RF signals to stimulate a targetemitter (e.g., based on MAC address of emitter) and captures responsesignals from the target emitter. Recall that the ‘response’ signals mayalso be provided automatically (without stimulus). The multi-elementantenna array 218 b is capable of providing coverage of the spectrum ofinterest in azimuth (horizontal field of view), and optionally inelevation (vertical field of view) and polarization (frequency), if sodesired. The RF switching network 218 a is configured to select elementsof the antenna array 218 b (based on control signals provided bycomputer 200) in synchronization with the transceiver 217. The jointoperation of transceiver 217 and beamformer 218 effectively forms beamsfor long range transmission/detection.

Each of the transceiver 217 and beamformer 218 can be implemented withcommercial off-the-shelf (COTS) equipment, such as a COTS 802.11transceiver and a multi-element beamformer. For example, in one specificembodiment, the multi-element beamforming array 216 (includingtransceiver 217 and beamformer 218) is implemented using a MediaFlex™access point produced by Ruckus Wireless, Inc. This commerciallyavailable beamformer has a clam-shell configuration and can be coupledto the system 10 via an Ethernet connection. In another exampleembodiment, the transceiver 217 and beamformer 218 may be implemented asdescribed in U.S. Pat. No. 7,362,280, which is incorporated herein inits entirety by reference.

The computer 200 can be implemented with conventional technology,including display area 201 b (e.g., LCD display), processor 203 (e.g.,Intel® Pentium® class processors, or other suitable microprocessors),and memory 205 (e.g., any RAM, ROM, cache, or combination thereoftypically present in computing devices). However, as will be explainedin turn, the LOB module 207, calibration files 209, and geolocationmodule 211 are programmed or otherwise configured to carryoutfunctionality described herein. Likewise, user controls provisioned forthe user interface 201 (such as controls 201 a) may be programmed orotherwise configured to control and/or task the system 10 to carryoutfunctionality described herein. In some specific embodiments, thecomputer 200 can be implemented, for example, with a miniature orso-called ultra mobile computer, such as the OQO model 2+ produced byOQO, Inc., or the VAIO® UX Series Micro PC produced by Sony Corporation.Any number of small portable computing platforms can be used toimplement computer 200.

The LOB module 207 is programmed or otherwise configured to convert aresponse signal from transceiver 217 into a line of bearing (LOB)relative to the current position and orientation of array 218 b. Thegeolocation module 211 is programmed or otherwise configured to identifythe actual location of the target emitter on the LOB, based on theintersection of LOBs from multiple vantage points (e.g., on a mapdisplay) and/or GPS position and heading tags associated with eachcomputed LOB. For instance, in the example embodiment shown in FIG. 2 a,the system includes GPS module 213 and its corresponding antennas 213a-b, so that each LOB to a target device can be associated with positionand heading tags. The GPS module 213 and antennas 213 a-b can beimplemented with conventional GPS receiver and antenna technology. Inone example embodiment, GPS module 213 is implemented with a Crescent®Vector OEM board produced by Hemisphere GPS, Inc. This particular GPSboard, which can be operatively coupled to computer 200 by an RS-232serial port or otherwise integrated into computer 200, provides a GPScompass and positioning system that computes heading and positioningusing two antennas for greater precision. Other suitable GPS receiverscan be used as well, as will be apparent in light of this disclosure. Inany such cases, the geolocation module 211 accumulates bearings providedby GPS module 213 to produce a geolocation, which can then be provided,for instance, on a map display.

The user interface 201, including controls 201 a and display 201 b,allows the user to control and task the system 10. In one specific case,the LOB results can be mapped or shown on a polar plot to indicate inreal time the direction to the target emitter. The user interface 201may include, for example, a probe button that when pressed or otherwiseselected initiates transmission of a stimulus signal by the transceiver217 and beamformer 218 to a target device, so that the signal response(or other signal, whether provided automatically or in response tostimulus) from the device can be received at the antenna array 218 bover multiple antenna configurations to provide a sample array ofresponse data for that device. The multiple antenna configurations canbe selected, for example, automatically by the control provided to thetransceiver 217 and beamformer 218 by computer 200, or by operation ofthe beamformer 218 itself. The array of response data can then beanalyzed by the LOB module 207 to identify an LOB to the target device.In addition, the computer 200 may be configured to direct transceiver217 to transmit a specific stimulus signal having parameters customizedto a given target device. In any such cases, the computer 200 receivesthe response signals from transceiver 217 for processing by the LOBmodule 207. The geolocation module 211, whether present in the samesystem 10 or remote to system 10, can then compute a specific locationbased on the computed LOBs from different vantage points.

Each of the modules 207 and 211 can be implemented, for example, as aset of instructions or code that when accessed from memory 205 andexecuted by the processor 203, cause direction finding and geolocationtechniques described herein to be carried out. In addition, the userinterface 201 can be programmed or otherwise configured to allow forfunctionality as described herein (e.g., wherein controls 201 a areimplemented as graphical user interface with touch screenfunctionality). The calibration files 209 effectively make up entries ina database that can be, for example, any suitable data storage populatedwith gold-standard response data having a known azimuth to which testdata can be correlated. The gold-standard response data may be, forinstance, empirical data measured by the system 10 in a multipathenvironment under known conditions (e.g., where the azimuth/LOB from theantenna array 215 b to the target emitter device 50 is known, and a fullset of calibration measurements are taken at each known azimuth).Alternatively, the gold-standard response data can be theoretical data(assuming the theoretical data is sufficiently accurate to provideaccurate results). In any such cases, the database 209 can be populatedwith gold standard data for any number of azimuths. The number ofazimuths represented in the database 209 can vary depending on factorssuch as the desired azimuthal resolution and FOV. In one exampleembodiment, the FOV is assumed to be 360° with a desired resolution of1° (i.e., 360 azimuths). Other embodiments may have a narrower FOVand/or a finer resolution (e.g., an FOV of 360° and a resolution of0.1°, wherein there are 3600 azimuths; or an FOV of 180° and aresolution of 1°, wherein there are 180 azimuths; or an FOV of 360° anda resolution of 20°, wherein there are 18 azimuths; or an FOV of 90° anda resolution of 2.0°, wherein there 45 azimuths. As will be appreciatedin light of this disclosure, the azimuthal resolution and FOV willdepend on the particular demands of the application at hand. The azimuthentry in the database having the calibrated array of data that bestmatches or otherwise correlates to the measured array of data directlycorresponds to the LOB to the target device associated with the measuredarray of data.

In other embodiments, the calibration files 209, each of the modules 207and 211, and any graphical user interface (GUI) such as controls 201 a,can be implemented in hardware such as purpose-built semiconductor orgate-level logic (e.g., FPGA or ASIC), or otherwise hard-coded. In otherembodiments, calibration files 209, modules 207 and 211, and GUI 201 amay be implemented with a combination of hardware and software, such aswith a microcontroller having input/output capability for providingcontrol signals to transceiver 217 and beamformer 218, and for receivingresponse data from transceiver 217, and a number of embedded routinesfor carrying out direction finding and geolocation techniques describedherein.

As previously explained, the network detector 215 and its omni-directionantenna 215 a can be used to carryout a covert or otherwise transparentsurvey process to identify various wireless emitters in the FOV ofsystem 10. In one such embodiment, the network detector 215 isimplemented with KISMET software executing on processor 203 of computer200. The omni-directional survey antenna can be implemented, forexample, with a Wi-Fi (802.11b/g) PCMCIA card (e.g., whip antenna) thatis operatively coupled to computer 200, or otherwise integrated intocomputer 200 to provide wireless connectivity. The detector 215 detectsand interprets information being transmitted by wireless emitters in theFOV, and identifies information such as MAC address, SSID, channel, andcurrent encryption status to be identified. Any number of networkdetectors can be employed for this surveying purpose.

The optional mapping module 221 b can be used to provide map displaysupon which computed LOBs and/or geolocation markers can be overlayed orotherwise integrated, so as to allow a visual display that can be usedin tracking the person associated with the targeted wireless emitterdevice 50. In one such embodiment, the mapping module 221 is a satellitebased mapping system (e.g., Google Earth™ mapping service) executing ona secondary computer system (e.g., laptop similar to computer 200,configured as a command workstation, along with the geolocation module211). Alternatively, the mapping module 221 can be implemented on acomputer 200. In one such case, the display area 201 b of the userinterface 201 provides a map display area having LOBs from multiplevantage points overlayed thereon (assuming a moving system 10, ormultiple systems 10 each deployed at a distinct vantage point). Otherinformation may also be included, as will be discussed with reference toFIG. 4.

The Ethernet hub 219 can be implemented with conventional technology,and operatively couples various components of system 10 to effectivelyprovide a communication network by which those components cancommunicate. In the example embodiment shown, each of computer 200,mapping module 221, and multi-element beamforming array 216 are coupledto the Ethernet hub 219 by respective Ethernet ports provided with each.Any number of conventional networking/connectivity technologies can beused here to operatively couple the components of system 10, andembodiments are not intended to be limited to Ethernet based solutions.

FIG. 2 b illustrates further details of the wireless emitter locatingsystem 10 shown in FIG. 2 a, with respect to the geo module 211 and theLOB module 207, in accordance with an embodiment of the presentinvention. As can be seen, the geo module 211 includes a geo computemodule 211 a and a SQL database 211 b, and the LOB module 207 includes ascan scheduler 207 a and an LOB compute module 207 b. In general,computing multiple LOBs as the system 10 is actively moving (such as thecase of a handheld or vehicle-based system 10) gives rise to varioustiming issues and can generate a significant amount of data. Forinstance, example timing considerations may involve when the next surveyand/or target probe should take place and on what channels, and exampledata includes emitter detections, multiple LOBs, and correspondingnavigation data for each of a plurality of points along the travel pathof system 10. To this end, the scan scheduler 207 a directs schedulingof system 10 operations in response to user survey and probe commands(from user interface 201 a), and SQL database 211 b efficiently stores(and makes accessible) pertinent data to the system 10.

In more detail, the scan scheduler 207 a of this example embodiment isprogrammed or otherwise configured to direct the network detector 215 tosurvey the FOV of system 10 for wireless emitters. The scheduler 207 aspecifies the channel to survey. For instance, the scheduler maysequentially schedule scans for each available channel associated with agiven protocol (e.g., IEEE 802.11). The detector 215 provides anydetections for each such survey back to the scan scheduler 207 a, whichthen stores those detections (along with any pertinent learnedinformation, such as MAC address, channel, encryption status, etc) indatabase 211 b. Note that although SQL technology is used in thisexample, other suitable database technologies can be used as well. Oncethe survey is complete (or if the target devices are already known), thescan scheduler 207 a can then select any of the detected emitters (e.g.,based on MAC address or other suitable identifier selected by user viauser interface 201 a and indicated in the probe command), and instructthe LOB compute module 207 b to compute an LOB for that particularemitter at that current location of the system 10. For each LOB providedby module 207 b to scheduler 207 a, the scheduler 207 a queries thedatabase 211 b for navigation data at that particular time (time X). Ascan be further seen, the database 211 b responds by sending thescheduler 207 a the appropriate navigation data. The scheduler 207 athen stores the LOB along with its corresponding navigation data to thedatabase 211 b. The scheduler 207 a may repeat this processperiodically, so as to provide a continuous LOB from the vantage pointof that particular system 10 (which effectively allows the emergencyresponder or other person associated with the targeted emitter to betracked, particularly when multiple deployed systems 10 are providingcontinuous LOB measurements). In the example embodiment shown, scanscheduler 207 a also directs the beamforming array 216 in conjunctionwith module 207 b. In alternative configurations, module 207 b candirect beamforming array 216 after scheduler 207 a instructs module 207b. Additional details of how module 207 b operates and interacts withthe cal files 209 and beamforming array 216 are provided with referenceto FIGS. 5 a-c.

As previously explained, the GPS module 213 provides current heading andposition data, which is also stored in the database 211 b and madeavailable the LOB module 207. The geo compute module 211 a is programmedor otherwise configured to compute, in response to a geolocate commandfrom the user (via interface 201 a), a geolocation for the specifiedtarget emitter. As previously explained, the geolocation can be computedbased on the intersection of the corresponding LOBs and/or thenavigation data (position/heading tags) associated with those LOBs. Aspreviously explained, in some embodiments, the geo compute module 211 acan be implemented in a command workstation that receives via a wirelessnetwork the LOBs and related data (GPS position and heading tags, timestamps, and other pertinent information) computed by a number of systems10 deployed at a scene where emergency responders or other personnel arepresent. By continuously computing geolocations to a target emitterbased on LOBs to that emitter from multiple vantage points, the personassociated with that emitter can be tracked so their precise location atany one time is known (even when that person is inside a building andnot visible from outside the building). The computed geolocations may bestored in the database 211 b by module 211 a, if so desired.

FIG. 2 c illustrates example states and modes of the wireless emitterlocating system 10 shown in FIG. 2 a, in accordance with an embodimentof the present invention. As can be seen, the diagram includes two mainportions: one for the computer 200 (which is a laptop in this example)and another for other hardware (detector 215 and array 216) of system10. At power-up, the system 10 transitions from its OFF state to itsOnline state, where upon the database 211 b becomes available andmodules 201 a and 213 come online. During an Offline/Editing state, onlythe computer 200 (with its modules and database 211 b) may be powered-on(e.g., leave module 213 powered-down or in low power mode to conservepower), which allows for offline tasks such as importing/exporting dataand computing of geolocations.

Once computer 200 is in its Online state, the user may task system 10hardware to survey, probe, etc. To conserve power, note that detector215 and array 216 can be powered-down or held in a low power mode duringextended periods of not receiving any user tasks. Once a task isreceived, the system 10 can transition from a Standby state to either aSurvey state or a Probe state, depending on the user task received. Forinstance, if the survey button (or other user interface mechanism) isselected, the system transitions to the Survey state where availablechannels are surveyed for wireless emitters. The channels to survey canbe automatically selected (e.g., by operation of scheduler 207 a aspreviously described), or specified by the user. In one such case, afterthe survey is complete, the user can select a new set of channels forsurvey, or set the channels list to 0 (i.e., no further surveying). Notethat, in some embodiments, surveying may not be necessary if each of thedeployed emitters is already known to the system 10.

As can be further seen, selecting the probe button (or other userinterface mechanism) causes system 10 to transition to the Probe statefor targeted probing of an emitter having a specified MAC address. Ifafter N seconds (e.g., 5 to 15 seconds) no response is received from thetargeted emitter, system 10 may transition back to the Survey state ineffort to identify other emitters in the FOV or to correct identifyinginformation associated with the target emitter. Alternatively, thesystem 10 can transition back to the Standby state. Any number oftiming/abort schemes for controlling state transition can be used here.

FIGS. 3 a and 3 b illustrate a vehicle-based version of the wirelessemitter locating system 10 shown in FIG. 2 a, configured in accordancewith an embodiment of the present invention. As can be seen, the system10 includes inside vehicle componentry 10 a (as best shown in FIG. 2 a),a multi-element beamforming array 216, GPS antennas 213 a-b, and surveyantenna 215 a as previously discussed with reference to FIG. 2 a, andthat previous discussion is equally applicable here. In addition tothese components, this embodiment further includes a mobile platform 311and cabling 307. The vehicle 310 can be any type of suitable vehiclegiven the particular application at hand (e.g., military vehicles oremergency responder vehicles), and numerous deployment schemes forsystem 10 will be apparent in light of this disclosure.

In this example embodiment, the platform 311 is used to support aclam-shell configuration that houses the multi-element beamforming array216. The cabling 307 is for operatively coupling the outer vehiclecomponentry to the inside vehicle componentry 10 a, and may include abound cable harness or a number of independent dedicated cablesoperatively coupled between respective components. The clam-shellassembly including the beamforming array 216 can be implemented, forexample, using a MediaFlex™ access point produced by Ruckus Wireless,Inc. As previously explained, the user interface 201 can be used to taskor otherwise activate system functions. Alternatively, the system 10 mayoperate automatically once deployed and powered up at a given scene, soas to provide continuous LOB data to wireless emitters in its FOV to acommand workstation that continuously computes, maps and displaysgeolocations based on those LOBs, to track location of target emitters.Any number of user interface and/or activation mechanisms may beimplemented to allow for control and/or tasking of the system 10, aswill be apparent in light of this disclosure.

FIG. 4 illustrates an example user interface 201 of the wireless emitterlocating system 10 shown in FIG. 2 a, in accordance with an embodimentof the present invention. As can be seen, the interface 201 isimplemented within a browser and includes a map display area fordisplaying multiple LOBs computed by the system 10 as well as thevehicle's path. In other embodiments where multiple systems 10 are eachdeployed at fixed locations (e.g., such as locations along the vehiclepath shown), a similar plot can be provided, where the multiple LOBs areprovided by multiple systems 10 as opposed to a moving system 10. In anysuch cases, map setting and information can also be provided, to allowthe user to configure the map as desired (e.g., to show more or fewdetails, zoom level, labels, etc).

In this example user interface, an LOB resulting from the processcarried out by LOB module 207 is visually depicted on a polar plot,along with the vehicle heading, to indicate in real-time the directionto the target device relative to the current position and orientation ofarray 216. As can be further seen, specific LOB details may also bedisplayed to ease the user's viewing, if so desired.

Also shown above the LOB polar plot are response signals and thecorresponding correlation factors computed by the system 10 as describedherein. As can be seen, each response signal parameter of amplitude (Am. . . ) that has been measured has an ID value and corresponds to acomputed correlation factor (Corr.) and a corresponding azimuthal (Az .. . ) value. The user may search this data and/or scroll the data forreview. In this specific example, the user can also specify a maximumLOB age (to prevent stale readings), if so desired.

The interface 201 of this example further includes a section for surveyresults showing discovered wireless emitters and correspondinginformation associated with each such emitter. The information includes,for instance, a callsign, SSID, type of emitter (e.g., 802.11b, 802.11g,etc), MAC address, communication channel, category (e.g., 0=unencrypted;1=encrypted), the number of LOBs computed for that emitter (if any),emitter ID (if assigned), and the client MAC (which may be helpful inembodiments where there is more than one system 10 providing informationas described herein and best shown in FIG. 6).

For instance, in one such embodiment, and assuming results from multiplesystems 10 are shown in the section for survey results (or the sectionshowing available emitters), the client MAC may be one of three or four(or more) systems 10 deployed at a scene. In one such case, the userinterface 201 is only provided at the command workstation (i.e., thesystems 10 computing and transmitting the LOBs and other pertinent dataneed not have displays or other user interfaces, so long as they publishthat LOB data to the mesh or other suitable network for receipt by thecommand workstation). Once the person operating the command workstationselects a particular system 10 for display (e.g., via touch screenselection), then the LOBs associated with that system 10 can be, forinstance, highlighted on the map display area. In addition, the lastcomputed LOB for that system 10 can be shown on the polar plot section,and the corresponding measurement data can be shown in the responsesignals and correlation factors section of the user interface 201. Anynumber of such user interface schemes can be used.

The interface 201 of this example further includes a Probe button (e.g.,touch screen activated or otherwise selectable by the user) forinitiating a probing task of a selected emitter device. The interface201 may also include a Survey button to initiate surveys. Otherembodiments may combine the tasking functions for Probing and Surveyinto a single button. The interface further includes a Geolocate button,which initiates a geolocation computation for a selected emitter basedon its LOBs and associated navigation data. As previously explained, thesystem 10 may simply operate automatically once deployed, and need notinclude a tasking interface.

Line of Bearing Determination

FIG. 5 a illustrates a method for determining an LOB to a wirelessemitter and geolocating that emitter based on multiple LOBs, inaccordance with an embodiment of the present invention. As previouslyexplained, the method can be carried out, for example, by one or moresystems 10 (e.g., with one configured as a command workstation fortracking target emitters, and others for computing LOBs and publishingthose LOBs to the command workstation).

The method begins with surveying 501 the area of interest to identifywireless emitters within that area (e.g., by MAC address, and/or othersuitable identifiers). The user can task this survey, for example, usingthe user interface 201 (e.g., survey button on graphical user interfacethat is coded to generate control signals commanding the transceiver 217and beamformer 218 to transmit the survey signal). Note that this stepmay be done contemporaneously with remaining portions of the method, orat any time prior to the remaining portions. Alternatively, thissurveying step may be carried out automatically (at power-up and/orperiodically thereafter), or not at all if wireless emitter devices arealready known.

The method continues with selecting 503 a target emitter discoveredduring the survey (e.g., based on the target device's MAC address orother suitable identifier, and using the channel associated with thatemitter) for probing to direction find and geolocate that emitter. Theuser can task this probing of the target device, for example, using theuser interface 201 (e.g., user can select the target emitter usinggraphical user interface that is coded to display a list of emittersidentified during the survey, and then user can select probe button ongraphical user interface that is coded to generate control signalscommanding the transceiver 217 and beamformer 218 to transmit the probesignal). Alternatively, the selecting can be automatic, such that themethod includes systematic and periodic probing of available wirelessemitters based on a pre-set tracking schedule.

The method continues with transmitting 505 a stimulus signal to thetarget emitter. Recall that computer 200 of system 10 may be configuredto direct transceiver 217 to transmit a specific stimulus signal havingparameters customized to a given target device, if so desired (e.g., ascommanded by LOB module 207). Alternatively, the stimulus signal can beany signal that causes the target emitter to provide a response signalthat can be detected and processed by system 10 as described herein.Recall that no stimulus signal is required in instances where a giventarget device automatically broadcasts or otherwise transmits itsinformation (such voluntary signals can be considered a ‘response’ aswell, for purposes of this disclosure). In such cases, the systemexecuting the method can passively listen for target emittertransmissions.

The method continues with measuring 507 the response signal parameter(or parameters) for each of Y antenna patterns, thereby providing a Ysample array of response data. As previously explained, the antennaarray 218 b is configured with a number of elements that can be selectedby switching network 218 a to provide various antenna configurations. Inone example case, the antenna has six horizontally-polarized elements,thereby providing 2⁶ different configurations (i.e., Y=64). In anotherexample case, the antenna has six horizontally-polarized andvertically-polarized elements, thereby providing 2 ¹² differentconfigurations (i.e., Y=4096).

The method continues with correlating 509 the sample array to aplurality of entries in a database of calibrated arrays having knownazimuths, to generate a correlation plot. This process can be carriedout, for example, by the LOB module 207, or a dedicated correlationmodule. As is generally known, a correlation process measures how welltwo populations match one another. Any conventional correlationtechnique can be used to perform this correlation, where such techniquestypically provide a correlation factor between 0 (low correlation) and 1(high correlation). FIG. 5 b illustrates a correlation process toidentify which calibrated array best matches a sample array, inaccordance with an embodiment of the present invention. As can be seen,the cal files 209 include 360 calibrated arrays, one for each LOBranging from 1° to 360° (with a 1° resolution). In this example of FIG.5 b, the antenna array has two elements capable of providing fourdistinct antenna patterns (indicated as 0,0; 0,1; 1,0; and 1,1). Thus,once the sample array of response data is provided by the transceiver217 to the computer 200, that sample array can be compared against thecal files 209 to generate a correlation factor for each comparison. Eachof these correlation factors can then be plotted to provide acorrelation scan or plot as shown in FIG. 5 c. The peak of thecorrelation plot corresponds to an azimuth (or LOB) to the targetemitter. Note that LOB is effectively interchangeable with azimuth inthis context.

The method therefore continues with identifying 511 the target azimuthof the sample array based on the peak of the correlation plot, anddetermining a line of bearing (LOB) to target based on the targetazimuth. In the example of FIGS. 5 b and 5 c, the sample array bestmatches the cal file 209 corresponding to the LOB of 280°. As will beappreciated, the number of azimuths and antenna patterns used for thisexample was selected for ease of depiction. Other embodiments may haveany number of azimuths (represented in cal file 209) and/or antennapatterns. In any such case, the target LOB can be graphically displayedto the user (e.g., as shown in FIG. 4).

The method continues with geolocating 515 the target emitter based ontwo or more LOBs, from multiple vantage points. In one such embodiment,this geolocation is carried out by the user moving to a second locationand then repeating steps 505 through 513 to get a second LOB to target.The user may repeat at any number of additional locations, providing anLOB at each location. The user may collect such LOBs at multiple points,for instance, along an L-shaped path, or other path that will allow forgeolocation based on LOBs to be carried out. Alternatively, a pluralityof systems 10 can be deployed, each at a respective vantage point(effectively having the same results as a mobile single system 10). Inany case, the computed LOBs can be stored, for example, in a memory ofeach computer 200 or only in a command workstation, and/or displayed tothe user as shown in FIG. 4 (along with travel path and/or multiplevantage points and system 10 locations). Alternatively, the user canmanually plot the LOBs. In any such cases, the LOBs will generallyintersect. The more LOBs provided to the target, the more robust andaccurate the intersection will be. The user can then translate thisintersection to a geographic location, using conventional geolocationtechniques. As previously explained, each LOB may be further associatedwith position and heading data (from navigation system), which can alsobe used to readily and accurately geolocate the target emitter.

Personnel Tracking System

FIG. 6 illustrates a system for direction finding, geolocating, andtracking emergency personnel, configured in accordance with anembodiment of the present invention. In a more general sense, the systemcan be used to track people (or animals, or other items) in any numberof tracking applications, as will be apparent in light of thisdisclosure.

As can be seen, the tracking system is deployed at the scene of aburning building and includes a number of wireless emitter locatingsystems 10. In this particular example scenario, system 10 a is locatedon a fire truck, system 10 b is located on an ambulance, system 10 c islocated on a police car, and system 10 d is configured as an incidentcommander workstation. Any number of emergency responder vehicles orother vehicles can be configured with systems 10. Likewise, othersystems 10 may be brought to the scene in a suitcase (such as thecommand workstation) and/or a handheld unit. An example handheld unit isprovided in the previously incorporated U.S. application Ser. No.12/487,469. Each of the systems 10 communicates with one another via awireless network (e.g., mesh network). The tracking system is configuredfor tracking the movement of a first responder (a fireman in thisexample), who has a wireless emitter (e.g., sewed into coat of fireman,or fireman's personal cell phone). The emitter can be, for example, anIEEE 802.11 emitter.

In operation, the incident commander's workstation system 10 d receivesinformation published to the wireless network by the other systems 10a-c. The published information includes, for example, LOBs to thefireman which are periodically computed (e.g., every 1 to 15 seconds) byeach system 10 as well as time stamps and GPS location data associatedwith those LOBs. In the moment depicted in FIG. 6, system 10 a hascomputed and published LOB 1, system 10 b has computed and published LOB2, and system 10 c has computed and published LOB 3. Each of systems 10a-c can compute the LOBs as previously described (e.g., with referenceto LOB module 207). The system 10 d receives the published informationfrom the mesh network, and periodically computes (e.g., every 1 to 15seconds) geolocations of the fireman, and then publishes that locationon a map (e.g., user interface 201). In one example case, theintersection of the three LOBs is calculated in 3D and plotted on a 3Dmodel of the burning building. Any display that allows the fireman to belocated can be used.

The wireless network can be implemented with any number of suitableconventional technologies. In one example embodiment, the network isimplemented with a First InterComm™ mesh network produced by BAESystems. The First InterComm™ system allows radios operating ondifferent frequencies and protocols to communicate with each other. TheFirst InterComm™ system unit can be mounted, for example, inside avehicle, and uses the responder's radio frequency, runs off thevehicle's battery, and requires no operator involvement.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthis disclosure. For instance, some embodiments are discussed in thecontext of a ground vehicle-based device. Other example embodiments maybe any vehicle-based (e.g., airplane, ship, etc). Still other exampleembodiments may be backpack-based, such that a user can don the backpackand control and task system using a wired or wireless remote having asmall display screen to allow user to see computed LOBs/geolocationresults. Alternatively, such a backpack-based system can be configuredto respond to voice commands, and aurally present computedLOBs/geolocation results so that user's hands remain free. It isintended that the scope of the invention be limited not by this detaileddescription, but rather by the claims appended hereto.

1. A method for tracking personnel at a scene, the method comprising:transmitting a stimulus signal to a target wireless emitter of a personto be tracked using a known physical address associated with that targetwireless emitter to stimulate a response signal from the target wirelessemitter; measuring one or more response signal parameters for each of Yantenna patterns, thereby providing a Y sample array of response datafrom the target wireless emitter, wherein Y is greater than 1;correlating the sample array to a plurality of entries in a database ofcalibrated arrays having known azimuths, to determine a line of bearing(LOB) to the target wireless emitter; repeating the transmitting,measuring and correlating to determine one or more additional LOBs tothe target wireless emitter, each LOB computed from a differentgeographic location; and geolocating the target wireless emitter basedon the LOBs, thereby geolocating the person.
 2. The method of claim 1further comprising the preliminary steps of: surveying an area ofinterest to identify wireless emitters within that area; and selecting atarget emitter discovered during the survey.
 3. The method of claim 2wherein the transmitting includes transmitting the stimulus signal tothe target emitter using a media access control (MAC) address andcommunication channel associated with the target emitter learned duringthe survey.
 4. The method of claim 1 wherein the correlating comprises:generating a correlation plot having a peak using correlation factorsresulting from correlation of the sample array to the plurality ofentries in the database; identifying a target azimuth of the samplearray based on the peak of the correlation plot; and determining the LOBto the target wireless emitter based on the target azimuth.
 5. Themethod of claim 1 wherein each of the LOBs is associated with positionand heading tags provided by a global positioning satellite (GPS) moduleto assist in geolocating the target wireless emitter.
 6. The method ofclaim 1 further comprising: graphically displaying geolocations of thetarget wireless emitter.
 7. The method of claim 1 further comprising:periodically repeating the geolocating of the target wireless emitter,thereby periodically geolocating the person as that person moves aroundthe scene.
 8. The method of claim 1 wherein there are 64 or 4096 antennapatterns.
 9. The method of claim 1 wherein the one or more responsesignal parameters include response signal amplitude.
 10. The method ofclaim 1 wherein the method is carried out using portable devicesconfigured for performing the transmitting, measuring and correlatingand a command workstation wirelessly coupled to the portable devices isconfigured for performing the geolocating.
 11. A system for trackingpersonnel at a scene, the system comprising: a switchable antenna arrayfor measuring one or more signal parameters for each of Y antennapatterns, thereby providing a Y sample array of signal data from atarget wireless emitter of a person to be tracked, wherein Y is greaterthan 1; a line of bearing module for correlating the sample array to aplurality of entries in a database of calibrated arrays having knownazimuths, to determine a line of bearing (LOB) to the target wirelessemitter; and a geolocation module for geolocating the target wirelessemitter based on multiple LOBs to the target wireless emitter, each LOBcomputed from a different geographic location, thereby geolocating theperson.
 12. The system of claim 11 wherein the system is furtherconfigured for surveying an area of interest to identify wirelessemitters within that area, the system further comprising: a userinterface for allowing a user to select a target emitter discoveredduring the survey.
 13. The system of claim 12 wherein the target emitteris associated with a media access control (MAC) address andcommunication channel learned during the survey, and the system furtherincludes a transceiver configured for transmitting a stimulus signal tothe target emitter using the MAC address and communication channel. 14.The system of claim 11 wherein the line of bearing module is configuredfor generating a correlation plot having a peak using correlationfactors resulting from correlation of the sample array to the pluralityof entries in the database, and identifying a target azimuth of thesample array based on the peak of the correlation plot, and determiningthe LOB to the target wireless emitter based on the target azimuth. 15.The system of claim 11 wherein each of the LOBs is associated withposition and heading tags provided by a global positioning satellite(GPS) module to assist in geolocating the target wireless emitter. 16.The system of claim 11 further comprising: a user interface forgraphically displaying geolocations of the target wireless emitter. 17.The system of claim 11 wherein the geolocation module is furtherconfigured for periodically geolocating the target wireless emitter,thereby periodically geolocating the person as that person moves aroundthe scene.
 18. The system of claim 11 wherein the system comprises aplurality of portable devices each located at a different vantage pointto the scene and configured with a transceiver and a switchable antennaarray and a line of bearing module, and the system further comprising acommand workstation wirelessly coupled to the plurality of portabledevices and configured with the geolocation module.
 19. The system ofclaim 11 wherein the target wireless emitter is associated with aphysical address, the system further comprising: a transmitter fortransmitting a stimulus signal to the target wireless emitter using thephysical address to stimulate a response signal from the target wirelessemitter, the response signal having the one or more signal parameters.20. The system of claim 11 wherein the switchable antenna array includesa plurality of elements, the system further comprising: a switchingnetwork for selecting the elements to provide each of the Y antennapatterns.
 21. The system of claim 20 wherein the switchable antennaarray includes both vertically-polarized and horizontally-polarizedelements.
 22. The system of claim 11 wherein the database has anazimuthal resolution of 1 degree or higher for a field of view of viewthat includes the scene.
 23. A system for tracking personnel at a scene,the system comprising: a user interface for allowing a user to select atarget emitter of a person to be tracked, wherein the target emitter isassociated with a media access control (MAC) address and communicationchannel learned during the survey; a transceiver for transmitting astimulus signal to a target wireless emitter using the MAC address andcommunication channel; an antenna array for measuring one or moreresponse signal parameters for each of Y antenna patterns, therebyproviding a Y sample array of response data from the target wirelessemitter, wherein Y is greater than 1, and the one or more responsesignal parameters include response signal amplitude; a line of bearingmodule for correlating the sample array to a plurality of entries in adatabase of calibrated arrays having known azimuths, to determine a lineof bearing (LOB) to the target wireless emitter; a geolocation modulefor periodically geolocating the target wireless emitter based onmultiple LOBs to the target wireless emitter, each LOB computed from adifferent geographic location, thereby geolocating the person; and auser interface for graphically displaying geolocations of the person.24. The system of claim 23 wherein the line of bearing module isconfigured for generating a correlation plot having a peak usingcorrelation factors resulting from correlation of the sample array tothe plurality of entries in the database, and identifying a targetazimuth of the sample array based on the peak of the correlation plot,and determining the LOB to the target wireless emitter based on thetarget azimuth.